1. Field of the Invention
The present invention relates to an apparatus for taking a liquid content for use in analysis out of a container including a container main body having an opening and a cap secured hermetically to said opening to keep an inside of the container main body at a reduced or negative pressure.
2. Description of the Related Art Statement
In a chemical or biological analyzing system, a liquid content such as various kinds of samples derived from patients and reagents are usually contained in a container comprising a container main body having an opening and a cap hermetically is secured to the opening to keep the inside of the container main body. In order to store such a liquid content reliably, the liquid content is sometimes dried and dried substances are contained in the container. Upon usage, a solvent is added to form a solution and a given amount of the solution is taken out of the container. Apparatuses for taking a liquid content out of Such a container may be roughly classified into the following two types. In a first type, at first the cap is removed from the container main body, and then the liquid content is taken out of the container by inserting the suction nozzle into the container main body via the opening. In a second type of the apparatus, a suction nozzle having a tip in the form of a needle is inserted into the container main body by piercing the needle through the cap made of rubber and the liquid content is sucked into the suction nozzle.
In a blood analyzing system, a sample blood has to be taken out of a patient into a blood collection tube having a rubber cap. When the sample blood is collected from the patient, use is generally made of a vacuum type blood collection tube. In this type of blood collection tube, the inside of the tube is kept at a negative pressure and a sample blood is sucked into the tube effectively. After the sample blood has been sucked into the tube, the inside of the tube is still maintained at a negative pressure. Therefore, when the rubber cap is removed from the blood collection tube in order to take the sample blood out of the blood collection tube, the pressure inside the tube is abruptly increased from the negative pressure to the atmospheric pressure, so that the sample blood might be spread or overflowed from the tube. Then, an amount of the blood sample remained in the tube becomes small and a given amount of the sample blood could not be taken out. In this connection, it should be noted that nowadays test items to be analyzed for the sample blood has become larger, so that the collected blood sample has to used efficiently. Thus, when a part of the collected blood sample is overflowed from the blood collection tube, all the test items to be denoted for the sample blood could be no more performed. Moreover, since the pressure inside the tube varies during the operation for removing the rubber cap from the tube, control of a force for performing a punctual removal of the rubber cap in a determined time becomes very complex.
When the blood sample is taken out of the blood collection tube without removing the rubber cap, the suction nozzle having a needle secured to its distal end is inserted into the tube through the rubber cap such that the tip of the needle is immersed into the sample blood. After a given amount of the blood sample has been sucked into the suction nozzle, when the needle is removed out of the tube, an air is sucked into the needle, because the inside of the blood collection tube is maintained at the negative pressure. When the air is sucked into the needle and often makes undesired bubbles in the blood, an amount of the blood sample which is delivered from suction nozzle into a reaction vessel becomes smaller than a desired amount and the accuracy of the analysis is affected. Further, when the blood sample is sucked into the suction nozzle, the pressure inside the blood collection tube is reduced, and thus the control of the suction force for maintaining the accuracy of suction constantly becomes complicated.
When a serum of a sample blood is taken out of the vacuum type blood collection tube, the blood collection tube having the sample blood sucked therein is first set into a centrifugal apparatus and a serum and blood cells of the sample blood are separated from each other. Usually a separating agent mainly consisting of silicon is added to the blood sample. That is to say, the blood cells are collected into a lower portion of the tube as a clot and the serum is existent on the clot of blood cells. In order to take a given amount of the serum sample out of the tube, a suction nozzle is inserted into the tube through the rubber cap such that a tip of the serum sample sucking nozzle is immersed into the serum. However, a position of the tip of the suction nozzle in the serum is rather critical. When the suction nozzle is immersed into the serum deeply, undesired blood cells and separating agent might be sucked into the suction nozzle. Further the sucked blood cells and separation agent might clog the suction nozzle. On the contrary, when the suction nozzle is not sufficiently immersed into the serum, an amount of the sucked serum becomes smaller than a required amount. Moreover, an air might be introduced into the suction nozzle. Therefore, the suction nozzle has to be immersed into the serum such that its tip comes closer to a boundary between the clot and the serum. However, the position of the boundary between the clot and the serum varies for respective blood samples, so that it is necessary to detect the boundary. To this end, an assembly of a light source for emitting light and a photodetector for receiving the light emitted from the light source and transmitted through the blood collection tube is moved along a longitudinal axis of the tube. There is further proposed to use a sensor for detecting the position of the boundary by using light reflected by the boundary. However, usually on an outer surface of the blood collection tube there are provided a label on which patient number, edification number, patient name and so on are recorded and a bar code label. Sizes and positions of these labels on the tube differ widely from tube to tube. In some cases, a label is adhered around an entire surface of the tube. Therefore, it is very difficult to detect reliably the position of the boundary between the clot and the serum.
In order to detect the position of the boundary, there has been further proposed to measure an electrostatic capacitance or an electric resistance between electrodes which are secured to the tip of the suction nozzle and are immersed into the blood sample. However, such an electrical detection could not be performed reliably.
FIG. 1 shows a known apparatus for removing a rubber cap from an opening of a vacuum type blood collection tube. The apparatus comprises holding arms 2 for holding a vacuum type blood collecting tube 1 having an upper opening which is closed by a rubber cap 3 in a hermetical manner. The apparatus further comprises cap removing arms 4 which are arranged movably in a horizontal direction as well as in the vertical direction. On distal ends of the cap removing arms 4 there are secured pins 5 directing inwardly. After the tube 1 is held by the holding arms 2, the cap removing arms 4 are moved horizontally to come closer to each other and the pins 5 are penetrated into the rubber cap 3. Then, the cap removing arms 4 are moved upward to remove the rubber cap 3 from the tube opening. However, as stated above, the inside of the tube 1 is kept at the negative pressure, it is rather difficult to remove the rubber cap 3 only by moving the removing arms 4 upward. Therefore, an assembly of the cap removing arms 4 is arranged to be swingable about an axis which extends vertically to a plane of the drawing of FIG. 1 by means of any suitable swinging mechanism. When the cap removing arms 4 are swung, the rubber cap 3 is deformed to form a thin space between the cap and the tube so that an air is introduced into the tube 1 and the pressure inside the tube is gradually increased. In this manner, the rubber cap 3 can be removed from the blood collection tube 1.
In the known rubber cap removing apparatus shown in FIG. 1, it is necessary to swig the assembly of the cap removing arms 4, and this requires a very complicated swinging mechanism. Further when the tube 1 is made of glass, the tube is liable to be broken by the swinging movement.
Further, in the known apparatus, the pins 5 are inserted into the rubber cap 3, so that this apparatus could not be applied to other tubes which is made of other material or which is formed in different shapes.
In the chemical or biological analyzing system, the hermetically sealed container is generally vacuumed in order to avoid the evaporation of liquid substances, the oxidation of liquid or dried solid substances and the moisture absorption of dried substances. The dried substances are forming the powders by removing water and are stored in the container. When such dried substances are used, suitable solvent is supplied into the container to form a solution. Then a given amount of the solution is taken out of the container by either one of the above explained two methods. Such dried substances are enzymes, antigens and antibodies.
Further, the pressure inside the container may be reduced by providing the cap under the reduced pressure or by keeping the container at a low temperature after the cap is provided in the atmospheric pressure. In order to keep the reduced pressure reliably, a sealing member may be provided or the cap may be screwed into the opening of the container main body.
The container main body may be formed in any desired shape and the size-of the opening has be sufficiently wide for introducing the suction nozzle into the container main body through the opening. The container main body may be made of any desired material which has a substantially hermetic property in accordance with chemical and physical properties, environments under which the container is kept and the frequency of usages. When the liquid content is taken out of the container after the cap has been removed, the cap may be made of any desired material which has a substantially hermetic property. However, when the liquid content is taken by piercing the suction nozzle through the cap, the cap has to be made of material which has a substantially hermetic property and which affords the piercing of the suction nozzle. Usually the cap is made of natural or synthetic rubbers. In case of taking liquid contents from these containers, the above mentioned problems would equally occur.